Substrate positioning for deposition machine

ABSTRACT

A deposition device is described. The deposition device has a substrate support and a laser imaging system disposed to image a portion of a substrate positioned on the substrate support. The laser imaging system comprises a laser source and an imaging unit, and is coupled to a deposition assembly disposed across the substrate support.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 16/915,614, filed Jun. 29, 2020, which claims benefit of U.S.Provisional Patent Application Ser. No. 62/872,501 filed Jul. 10, 2019,each of which is incorporated herein by reference in its entirety.

FIELD

Embodiments of the present invention generally relate to depositiondevices. Specifically, deposition devices having an attached but movableservice platform are described.

BACKGROUND

Deposition by Inkjet deposition is common, both in office and homeprinters and in industrial scale printers used for fabricating displays,deposition of large scale written materials, adding material tomanufactured articles such as printed circuit boards, and constructingbiological articles such as tissues. Most commercial and industrialinkjet deposition machines, and some consumer printers, use dispensersto apply material to a substrate. The dispenser ejects a controlledquantity of deposition material toward a substrate at a controlled timeand rate so that the deposition material arrives at the substrate in atarget location and makes a mark having a desired size and shape.

In some cases, such as in the display fabrication industries, very highprecision deposition is achieved by depositing very small volumes ofmaterial at very precise locations. The volumes may have dimension of 10μm in some cases and may be deposited in an area of dimension 15 μm. Toachieve such precision in placement of materials on a substrate, thesubstrate must be positioned precisely and/or the position of thesubstrate must be known precisely. Vision systems using cameras areroutinely used to photograph a substrate and determine its positionprecisely, but capturing the images and processing the images is timeconsuming. There is a need for a better way to precisely determine theposition of a substrate for inkjet printing.

SUMMARY

Embodiments described herein provide a deposition device, comprising asubstrate support; and a deposition assembly comprising a laser imagingsystem disposed across the substrate support.

Other embodiments described herein provide a method of imaging a featureon a substrate, comprising scanning the substrate relative to a laserimaging system comprising a laser source and an imaging unit; activatingthe imaging unit before an extremity of the feature reaches anillumination field of the laser source; activating the laser source whena portion of the feature reaches the illumination field; deactivatingthe laser source after an active time; and deactivating the imagingsource after an imaging time, wherein the imaging time encompasses theactive time.

Other embodiments described herein provide a deposition device,comprising a substrate support; and a deposition assembly comprising alaser imaging system disposed across the substrate support, the laserimaging system comprising a laser source fiber coupled to an opticalassembly to direct laser radiation from the laser source toward thesubstrate support; and an imaging unit disposed to capture laserradiation reflected through the optical assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, may admit to other equally effective embodiments.

FIG. 1 is an isometric top view of a deposition device according to oneembodiment.

FIG. 2 is a block diagram of a position acquisition system according toone embodiment.

FIG. 3 is an algorithm diagram of a droplet ejection algorithm accordingto one embodiment.

FIG. 4 is a flow diagram of a method according to one embodiment.

FIG. 5 is a flow diagram summarizing a method that can be used with theapparatus and other methods described herein.

FIG. 6 is an isometric top view of a deposition device according toanother embodiment.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

A deposition device is described herein with a service platform that canbe deployed above the work surface of the deposition device and stowedadjacent to an end of the work surface at an elevation at leastpartially below a basis elevation of the work surface to allow forsubstrate loading and unloading. FIG. 1 is an isometric top view of adeposition device 100 according to one embodiment. The deposition devicehas a substrate support 102, a deposition assembly 104, and a holderassembly 106 for manipulating a substrate for deposition. The depositiondevice 100 includes a base 108, which is typically a massive object tominimize vibratory transmissions to the operative parts of thedeposition device 100. In one example, the base 108 is a granite block.The deposition assembly 104 includes a deposition assembly support 116comprising a stand 120 on each side of the base 108 and a rail or beam117 extending between the stands 120 across the substrate support 102.

The substrate support 102 has a first section 102A, a second section102B, and a third section 102C between the first and second section 102Aand 102B. The first and second sections 102A and 102B are staging areasfor substrates entering and leaving the deposition device 100, while thethird section 102C is a work section for positioning the substrate forprocessing relative to the deposition assembly support 116. Thesubstrate support 102 has a work surface 110 along with means for makingthe work surface 110 substantially frictionless. Here, the work surface110 is a gas cushion table that provides a gas cushion, for example air,oxygen depleted air, dry air, nitrogen, or other suitable gas on whichthe substrate floats. The work surface 110 features a plurality of holes(not shown) that allow jets of gas to exit, thus providing an upwardforce to maintain a substrate at a desired elevation above the worksurface 110. Some of the holes may also allow controlled withdrawal ofgas from the gas cushion floating the substrate support to provideprecise local control of substrate elevation. In one embodiment, thethird section 102C has gas providing holes and gas withdrawing holes.The gas providing and withdrawing holes provide independent control ofgas in the gas cushion and therefore substrate float height above thesubstrate work surface 110.

The deposition assembly 104 comprises a dispenser assembly 114 coupledto the beam 117. The dispenser assembly 114 includes a dispenser housing119 coupled to a deposition carriage 122 that rides along the beam 117to position the dispenser assembly 114 in relation to a substratedisposed on the third section 102C of the substrate support 102. Thedispenser housing 119 contains one or more dispensers (not shown) thateject volumes of deposition material onto a substrate positioned on thesubstrate support 102 under the deposition assembly 104.

A substrate is positioned under the deposition assembly 104 by theholder assembly 106. The holder assembly 106 acquires secure contactwith the substrate upon loading and moves the substrate along thesubstrate support 102 to position the substrate with respect to thedeposition assembly 104 for dispensing print material onto the substratein a precise fashion. The holder assembly 106, in this case, generallyextends along the substrate support 102 in a first direction totranslate the substrate in the first direction during deposition. Thefirst direction is denoted in FIG. 1 by arrow 124. The dispenserassembly 114 generally moves in a second direction substantiallyperpendicular to the first direction, as defined by the beam 117, whichextends substantially in the second direction, denoted in FIG. 1 byarrow 126. The second direction 126 is sometimes referred to as the “xdirection,” and the beam 117 as the “x beam.”

A controller 132 is operatively coupled to the holder assembly 106 andthe deposition assembly 104 to control movement of, and deposition onto,a substrate positioned on the substrate support. The controller 132 maydirectly control actuators of the holder assembly 106 and the depositionassembly 104, or the controller 132 may be operatively coupled to aholder assembly controller coupled to the holder assembly 106 and to adeposition assembly controller coupled to the deposition assembly 104.The controller 132 controls movement and positioning of the substrate,if any, on the substrate support 102. The controller 132 also controlsmovement of the dispenser assembly 114 along the beam 117 and ejectionof deposition material from the dispenser assembly 114 onto thesubstrate.

A laser imaging system 150 is coupled to the dispenser assembly 114. Thelaser imaging system 150 includes a laser source 152 and an imaging unit154. The laser source 152 directs laser radiation toward a substratepositioned on the substrate support 102 positioned under the dispenserassembly 114. The imaging unit 154 detects laser radiation reflectedfrom the substrate. The imaging unit 154 can include a digital camera orother high precision imaging capture component. The imaging unit alsoinclude optics for focusing the radiation into the image capturecomponent. The laser source 152 and imaging unit are arranged such thatthe laser source 152 provides an illumination field on the substratethat is within the imaging field of the imaging unit 154.

The laser source 152 may emit laser radiation that is selected tominimize impacts on other aspects of the deposition device 100 and theprocesses performed by the deposition device 100. For example, in manycases, curable materials are deposited on a substrate using thedeposition device 100. Such materials are routinely curable usingshort-wavelength electromagnetic radiation, such as ultravioletradiation. These materials are also, frequency, sensitive toshort-wavelength visible radiation, and can have minor sensitivity tolonger-wavelength visible radiation. Because uniform processing can beimportant to achieving the high precision results in industries such asthe display fabrication industry, the laser source can be selected toemit long wavelength radiation to minimize any impact on depositionmaterials. Laser sources having emission wavelengths of 650 nm or moreare useful in this regard. In one example, the laser source has emissionwavelength of 650 nm. In another example the laser source has emissionwavelength of 800 nm. The laser source can be a laser diode, orcollection of laser diodes such as a laser diode bar. The combination oflaser source and image capture component can also be selected tomaximize sensitivity of the image capture component to the radiationemitted by the laser source. For example, a Dalsa Nano M2020 camera hasnear-peak sensitivity at a wavelength of 650 nm. Silicon-based NIR imagecapture units typically have peak sensitivity around 800 nm.

The laser source 152 is, in this case, fiber coupled to translate thelaser emission to an emission plane that can be located close to thesubstrate. The divergence of the laser emission can thus be managed toproduce an illumination field having a desired dimension. For manydisplay applications, a substrate has a positioning feature, such as afiducial mark, that can be used to precisely calibrate the position ofthe substrate. The mark may be small, for example 1-5 mm in dimension.In some cases, the mark has a cross-shape. The fiber coupling allows theradiation emission plane to be positioned such that divergence of theradiation produces a spot that encompasses all, or a substantial partof, the view field needed to ascertain the position of a mark.

The laser imaging system 150 is configured to capture an image while thesubstrate and the dispenser assembly 114 move relative to one another.The relative movement can be as fast a 1 m/sec in some cases. An imagingcontroller 158 is operatively coupled to the laser source 152 and theimage capture unit 154 to drive image capture while relative movement isunderway. Here, the laser source has a pulse capability at least asshort as 5 μsec, meaning that the average intensity of the emittedradiation field increases, reaching half its maximum value at a pulsestart time, and decreases, reaching half its maximum value at a pulseend time, in a pulse duration, defined as the duration from the pulsestart time to the pulse end time, of about 5 psec. In some cases, alaser source having a pulse capability at least as short as 1 μsec isused. The imaging controller 158 is realized in a printed circuit boardcontaining the digital circuitry that communicates instructions to theimage capture unit 154 to start and stop image capture and to the lasersource 152 to switch on and switch off, or alternately to emit a pulsehaving a defined duration. The imaging controller 158 is operativelycoupled to the controller 132, and optionally to other controllers suchas holder assembly controllers and dispenser assembly controllers, tosend and receive signals representing information used to controlimaging of the substrate. The imaging controller 158 is configured tosend signals representing images captured by the imaging capture unit154 to the controller 132 for analysis. The imaging controller 158 isalso configured to control the image capture unit 154 and the lasersource 152 to capture an image when a feature of the substrate, such aspositioning feature, is expected to be within the field of view of theimage capture unit 154, based on information received, such as expectedposition of the feature and movement rate of the substrate, from thecontroller 132.

FIG. 2 is an elevation view of a position acquisition system 200according to one embodiment. The position acquisition system 200comprises the laser imaging system 150, with a substrate 202 disposed onthe substrate support 102 for processing. The laser imaging system 150is operatively coupled to the imaging controller 158, which is furtheroperatively coupled to the system controller 132, as described above.The laser imaging system 150 may also be operatively coupled to apositioning controller 204 that can control and adjust the position ofthe laser imaging system 150. The positioning controller 204 may adjustthe position of the laser imaging system 150 with respect to thedispensers of the dispenser housing 119 of FIG. 1 .

In this case, the laser imaging system 150 includes a laser source 206and an imaging unit 208. An optical assembly 210 optically couples thelaser source 206 and the imaging unit 208 to the substrate 202 forimaging. The optical assembly may include lenses and mirror fordirecting a focusing light reflected from the substrate into the imagingunit 208. An optical fiber 212 translates the laser radiation emitted bythe laser source 206 to an emission point 214, which may be at an end ofthe optical assembly 210 distal to the substrate support 102, may extendbeyond the end of the optical assembly 210 to a location closer to thesubstrate support 102 than the end of the optical assembly 210, or maybe recessed within the optical assembly 210. The optical fiber 212 issupported by a support 216 that maintains a position of the emissionpoint 214. Laser radiation is emitted from the optical fiber 212 at theemission point 214 and traverses a gap between the emission point 214and the substrate 202 to provide an illumination field 218. Dimension ofthe illumination field 218 can be controlled by controlling location ofthe emission point 214 with respect to the substrate 202. Duringprocessing, the substrate is typically scanned with respect to the laserimaging system 150 to illuminate portions of the substrate to be imaged,as indicated schematically by the arrow 220. The laser source 206 isactivated at times when the portion of the substrate to be imaged ispartially or completely within the illumination field 218 as therelative scanning is performed, and deactivated when the portion to beimaged has traversed the illumination field 218 for a time sufficient tocapture the desired image of the entire area to be imaged. This may bewhen a first portion of the area to be imaged exits the illuminationfield 218, or when a last portion of the area to be imaged exits theillumination field 218.

FIG. 3 is an algorithm diagram of an image capture control algorithm 300according to one embodiment. The image capture control algorithm 300 isused with deposition devices such as the device 100. The image capturecontrol algorithm 300 creates triggers for initiating image capture of afeature on a substrate 301 by an image capture unit and for initiatingillumination by an illumination unit. The illumination unit may be alaser, but is, in any event, capable of generating short pulses ofradiation within an illumination field. The duration of the pulses isaround 1 μsec, or shorter, to enable capturing images of a small featureon a substrate at relative rates of motion of up to 1 m/sec.

The algorithm 300 uses a position markers, along with position signalsfrom the substrate holder to determine when to begin image capture bythe image capture unit and when to begin illumination by the lasersource. Generally the algorithm uses a defined coordinate system that isused by the controller to perform the algorithm 300. The substrate has adefined origin point 302, which is positioned at a known position(x_(s), y_(s)) relative to a home position 304 of the holder (x_(H),y_(H)), which is also known. A design location 306 of a feature on thesubstrate (x_(F), y_(F)) is known relative to the origin point 302 ofthe substrate. In an embodiment where the substrate is moved in they-direction during processing, the y-position of the holder, substrateorigin, and feature are y_(h), y_(s), and y_(f), respectively. These areoffset from their various home positions in the y-direction by anidentical distance 308. If the laser imaging system is moved duringprocessing, the position of the illumination field 310 at any time isy_(i). The feature has design dimension of Δx_(F) and Δy_(F). Theillumination field 310 produced by the laser imaging system has a knownlocation (x_(l), y_(l)) relative to the holder home position. Theillumination field also has dimensions Δx_(l) and Δy_(l). Thus, in they-direction, the illumination field extends from

${y_{I} - {\frac{1}{2}\Delta y_{I}{to}y_{I}} + {\frac{1}{2}\Delta y_{I}}},$

or if the laser imaging system is moved,

$y_{i} - {\frac{1}{2}\Delta y_{I}{to}y_{i}} + {\frac{1}{2}\Delta{y_{I}.}}$

At any time during a process, the holder y-position y_(h) is known fromactuator position.

The various position markers are provided to a controller, such as thecontroller 132. The algorithm determines when to activate the imagecapture unit and the laser source to capture an image of the feature,based on the expected location of the feature. The size of theillumination field is set to provide sufficient coverage that any offsetbetween the expected position of the feature and the actual position ofthe feature is less than an amount that keeps the entirety of thefeature in the illumination field during the exposure.

Let relative movement velocity of the substrate and the laser imagingsystem in the y-direction be v, and let pulse duration be t. Thealgorithm computes a light-on event to illuminate the feature 306. Thelight-on event may be computed when the entire feature 306 is within theillumination field 310. This occurs when, in the y-direction,

${y_{f} - {\frac{1}{2}\Delta y_{F}}} = {y_{i} - {\frac{1}{2}\Delta{y_{I}.}}}$

If the holder position is offset in the y-direction relative to thesubstrate origin by y_(Hs) then the holder position at light-on time is

$y_{i} - {\frac{1}{2}\Delta y_{I}} - y_{f} + {\frac{1}{2}\Delta y_{F}} + y_{S} + {y_{HS}.}$

The light-on event can be computed in terms of holder position, time, orany other parameter that can be determined from the parameters of thedeposition job. If the light-on event is render as a time, it will bethe time at which

${vt} = {y_{i} - {\frac{1}{2}\Delta y_{I}} - y_{f} + {\frac{1}{2}\Delta{y_{F}.}}}$

The duration light is on is minimized to avoid distortion of the image.The substrate and the laser imaging system may be relatively moving whenthe image is captured. Illuminating the scene longer than necessary tocapture the desired image could result in reduction in the clarity ofthe image. The algorithm computes a light-off event when, after thelight-on event, the feature has traversed the illumination field. Thisoccurs when, in the y-direction

${y_{f} + {\frac{1}{2}\Delta y_{F}}} = {y_{i} + {\frac{1}{2}\Delta{y_{I}.}}}$

The algorithm 300 can compute light-off holder position as

$y_{i} + {\frac{1}{2}\Delta y_{I}} - y_{f} - {\frac{1}{2}\Delta y_{F}} + y_{S} + y_{HS}$

or the time at which

${vt} = {y_{i} + {\frac{1}{2}\Delta y_{I}} - y_{f} - {\frac{1}{2}\Delta{y_{F}.}}}$

The duration of the pulse is selected to be the time for the feature totransit the illumination field, which is

$t = {\frac{1}{v}{\left( {{\Delta y_{I}} - {\Delta y_{F}}} \right).}}$

The laser imaging system is positioned such that the x-position of theillumination field is the same as the designed x-position of thefeature.

FIG. 4 is a flow diagram summarizing a method 400 of capturing an imageof a position feature on a substrate. At 402, a substrate is positionedon a substrate support of a processing apparatus. Typically theprocessing apparatus is used to perform a process, such as materialaddition to, or removal from, the substrate, and positioning features ofthe substrate are used to guide the process. The position feature may bea special feature, such as a mark or structure, added to the substratespecifically for positioning the substrate, or the position feature maybe a feature added to the substrate for some other purpose and used herefor positioning the substrate.

At 404, the substrate is positioned to be photographed by a laserimaging system. The substrate can be moved into position with respect tothe laser imaging system by applying a substrate holder to move thesubstrate. In some cases, the substrate support includes a frictionlesssurface such that the substrate holder can move the substrate withlittle resistance. The laser imaging system can also be moved in somecases. For example, the laser imaging system may be deployed on apositioning system using an air bearing coupled to a rail. The laserimaging system includes a laser source oriented to direct laserradiation toward an imaging area. An imaging unit is positionedproximate to the laser source to image laser radiation reflected fromthe substrate.

The substrate is positioned for imaging at a location determined by anexpected location of the positioning feature. The expected location ofthe positioning feature is a pre-determined location on the substratewhere the positioning feature is expected to be found. The laser imagingsystem and the substrate are mutually positioned such that the expectedlocation is near an illumination field of the laser source.

At 406, the substrate is scanned with respect to the laser imagingsystem. The expected location of the positioning feature is moved towardan edge of the illumination field of the laser source. When the expectedlocation is at a pre-determined distance from the edge of theillumination field, the imaging unit is activated to begin acquiringimage data. At this time, the laser source is not active. Typically, theprocessing apparatus has an enclosure that isolates the substratesupport and laser imaging system, so any light source other than thelaser source is minimal.

At 408, the laser source is activated when an image of the positioningfeature can be captured by the imaging unit. The laser source may beactivated when a portion of the positioning feature is expected to enterthe illumination zone, when a fraction of the positioning feature insidethe illumination field of the laser source is expected to be at amaximum, or when the entire positioning feature is initially expected tobe within the illumination field of the laser source. In one case, thelaser source is activated when a leading edge of the positioning featureis expected to reach an edge of the illumination field. The expectedposition of the positioning feature may be at an extremity of thepositioning feature, or at a center of the positioning feature. If theexpected position of the positioning feature is at an extremity thereof,the laser source can be activated when the expected position of thepositioning feature is expected to reach the edge of the illuminationfield. If the expected position of the positioning feature is at acenter thereof, a known dimension of the positioning feature can be usedto determine an expected position of an extremity of the positioningfeature, and the laser source can be activated when the expectedposition of the extremity of the positioning feature is expected toreach the edge of the illumination zone.

In other cases, the laser source can be activated when the positioningfeature, or a large portion thereof, is expected to be entirely withinthe illumination field of the laser source. In this case, the lasersource is activated when a trailing edge of the positioning feature isexpected to reach the edge of the illumination zone, as determined bythe known geometry and expected location of the positioning feature.Waiting until a maximum portion, or all, of the positioning feature iswithin the illumination field of the laser source to activate the lasersource minimizes exposure time for capturing the image, and thereforeminimizes movement of the substrate during image capture. Minimizingmovement of the substrate during image capture results in the sharpestimage.

At 410, the substrate and laser imaging system are mutually scanned suchthat the positioning feature, or a portion thereof, transits theillumination field of the laser source during a transit time. Thetransit time may be defined in a number of ways. In one case, thetransit time is a time between when a first extremity of the positioningfeature enters the illumination field of the laser source and the lastextremity of the positioning feature exits the illumination field of thelaser source. In another case, the transit time is a time between when alast extremity of the positioning feature enters the illumination field,wherein the positioning feature has no other extremities that enter theillumination field thereafter, and a time when a first extremity of thepositioning feature exits the illumination field. In either case, all oronly a portion of the positioning feature may transit through theillumination field. The time during which the transit takes place may beas little as 1 μsec. The transit time can be determined using a knowndimension of the illumination field and by the velocity of transit.

At 412, the laser source is deactivated. An active time of the lasersource is defined as the time between when the laser source is activatedand when the laser source is deactivated. The active time of the lasersource may be the same as the transit time, or different. The activetime of the laser source may be coincident and simultaneous with thetransit time, may overlap with the transit time, or may encompass thetransit time. In one case, the active time is coincident and overlappingwith the transit time. In another case, the active time is coterminousand overlapping with the transit time. In yet another case, the activetime is concurrent with the transit time, and can overlap with thetransit time or encompass the transit time. In any event the active timeand transit time are related to illuminate a desired portion of thepositioning feature during the transit time.

In the event an image of the entire positioning feature is desired, butcannot be captured in a single exposure, due for example to the size ofeither the illumination field of the laser source or the size of theimaging field of the imaging unit, the substrate and laser imagingsystem can be repositioned for a second exposure to capture anadditional portion of the positioning feature in a manner similar to themethod 400.

At 414, the imaging unit is deactivated. An imaging time can be definedas the time between when the imaging unit is activated and when theimaging unit is deactivated. The imaging time is longer than the activetime of the laser source, since obtaining short laser pulses is morestraightforward than obtaining useful exposures with short exposuretimes. In the embodiments described herein, the positioning features mayhave dimension on the order of 1 μm, and scan velocity of the substratemay be as much as 1 m/sec. Thus, in some cases images are captured in aduration of 1 μsec using the methods and apparatus described herein.Such short duration exposures are more readily accomplished using ashort laser active time of 1 μsec with a longer imaging time of 1 msecor more.

The method 400 may be repeated to image a plurality of positioningfeatures. In each case, an expected position of the positioning featureis known, and the substrate and laser imaging system are positioned toplace the expected position near the illumination field of the lasersource. It should be noted that, due to errors in placement of thesubstrate, errors in placement of the laser imaging system, errors inapplication of the positioning features to the substrate, and thermaldisplacements and distortions, an image taken using the expectedlocation of the positioning feature may not capture the desired image.In such cases, the captured image can be analyzed to determine magnitudeand direction of a position correction that can be applied. The method400 can then be repeated, applying the position correction before orduring performance of the method 400. Typically the expected position ofthe positioning feature is modified by the position correction prior torepeating the method 400, but a bias can also be applied to the positionof the substrate and/or the laser imaging system in addition to, orinstead of, modifying the expected position of the positioning feature.

FIG. 5 is a flow diagram summarizing a method 500 that can be used withthe apparatus and other methods described herein. The method 500 is amethod of determining position and orientation of a positioning featureof a substrate from a laser-illuminated image. At 502, an image of anarea of a substrate is obtained at a location where a positioningfeature is expected to be found. The image is obtained using the laserimaging system described herein.

At 504, a set of grid points is defined within the image. The gridpoints are defined by x-y coordinates in a common coordinate system withpoints in the image. That is, the image is taken by locating the imagingsystem at a point defined by coordinates. The geometry of the imagingsystem determines the coordinates of the boundaries of the image in thecoordinate system. The grid points are defined between the coordinatesof the boundaries of the image. Any number of grid points may be used,with more grid points being helpful when the positioning feature has amore complex shape.

The expected shape and size of the positioning feature is typically alsodefined by coordinates in the same coordinate system. For example,vertices of a polygonal positioning feature can be defined by an orderedset of coordinate pairs, where adjacent coordinate pairs define thelocations of vertices connected by edges. For non-polygonal shapeshaving curved contours, the coordinates may define adjacent points onedge contours of the shape. More points in the shape definition of sucha shape improve the shape definition by minimizing the error of assumedstraight edges between neighboring points.

At 506, for each grid point defined at 504, a plurality of lines isdefined through the grid point. The lines can be defined as a set ofcoordinate pairs representing each pixel of the image along the lines,or the lines can be defined as a set of end points. The number of linesis pre-determined based on the complexity of the shape being imaged, andmay be increased if a first performance of the method 500 yieldsunsatisfactory definition of the positioning feature in the image. Thelines are generally selected to cover a plane uniformly, for exampleradiating at equal angles from the origin point.

At 508, for each line defined at 506, a brightness change from pixel topixel of the image along the line is determined. For each pixel P¹ onthe line, defined by a coordinate pair (x_(p1), y_(p1)) belonging to theset of coordinate pairs defining the line, the brightness of the pixelB_(p1) is ascertained. The brightness B_(p2) of at least one neighboringpixel P² on the line, at coordinates (x_(p2), y_(p2)) is alsoascertained. The two brightnesses are subtracted, B_(p2)-B_(p1) todetermine brightness change at pixel P¹. Absolute value is typicallyused. This type of brightness change is “forward” brightness change.Alternately, “backward” brightness change, where P¹ is compared to thepreceding pixel P⁰, or “central” brightness change, where averagebrightness change from P⁰ to P¹ to P², can be used.

Brightness change is generally used to indicate where a boundary may belocated in the image. At 510, a pre-determined number of the highestbrightness change pixels, points along the line having the highestmagnitudes of brightness change, are recorded as candidates for a shapeboundary within the image. Operations 506, defining lines, 508,analyzing brightness changes along the lines, and 510, recording thelargest magnitude brightness changes, are repeated for all grid pointsdefined for the image. From this process, a set of points is acquiredrepresenting candidate points for defining the edge of the shapecaptured in the image.

At 512, the recorded points are analyzed to determine which points lieon the boundary of the image of the positioning feature. Any number ofshape recognition algorithms can be used to determine which points canbe used to define the location of the boundary edge of the shape in theimage. Selection of the algorithm can be influenced by the known shapeof the positioning feature. For example, if the shape is known to becircular, or nearly so, equality of distance from a point can be used asa search criteria. For more complex shapes, distance based signaturescan be computed in a matching algorithm. For example, test shapesbounded by the known shape and dimension of the positioning feature canbe defined by coordinates, and distances of the recorded points from thetest shape can be determined. The test shape can then be sought, withinthe constraints of the known shape and dimension, which minimizes thedistance statistic. The result of such search can be improved byexcluding statistical outliers to resolve a “best” score for each testshape, and the test shape with the best overall score can be identifiedas the likeliest representation of the shape in the image.

From such a best test shape, further refinement of the shape can beperformed. For example, if the test shape has boundaries defined bycoordinate pairs of pixels on the boundary, curvature metrics can beapplied pixel by pixel to improve the test shape fit to the recordedpoints. At 514, a set of coordinates is defined as representing aboundary of the positioning feature in the image based on the analysisof 512.

After the boundary of the positioning feature in the image is defined incoordinates, characteristics of the positioning feature in the image canbe determined. At 516, a centroid of the coordinates defining theboundary of the positioning feature can be computed as the “center” ofthe feature. This location can be recorded in the system as the actuallocation of the positioning feature on the substrate. Alternately, amaximum or minimum x-value and a maximum or minimum y-value can be usedas the location of the positioning feature. When the position is definedat 516, a position error of the positioning feature can be determined at518. The position error is the difference between the coordinates of thepositioning feature as defined from the image analysis and the expectedcoordinates of the positioning feature. This position error can be usedto adjust processing plans for the substrate.

At 520, a rotation error can be defined for the positioning feature. Arotation transformation can be applied to the coordinate set definingthe boundary of the positioning feature in the image. For example, arotation angle can be defined in radians, and an x-y shift of each pixelin the coordinate set defining the boundary of the positioning featurein the image can be defined based on radial coordinates of each pixel.After applying the rotation transformation, a difference between therotated coordinate set of the image boundary and the expected coordinateset of the positioning feature boundary can be computed. The degree ofrotation that minimizes the difference can be used as the rotation errorof the image. The rotation error may be computed before or afteradjusting for any position error identified at 518.

At 522, a mis-shape error can be defined for the positioning feature.The mis-shape error documents distortion of the positioning feature fromits expected shape. The mis-shape error, if not detected andcompensated, can drive processing errors introduced based on theassumption that the positioning feature is shaped properly. For example,if one corner of a square positioning feature is misplaced, such thatthe positioning feature is not quite square, the positioning feature maybe found and located, but it's location may be mis-recorded for theprocessing system based on the mis-shape. The mis-shape error istypically determined after compensating for any position error androtation error. A pixel-by-pixel error of the position- androtation-compensated image can be computed and recorded as the mis-shapeerror. The recorded location of the positioning feature, for purposes ofprocessing the substrate, can be adjusted based on the identifiedmis-shape error.

The method 500 can be used to locate and define a plurality ofpositioning features of a substrate. Errors detected in a plurality ofpositioning features can be analyzed to identify systematic errors inplacement and orientation of a substrate in the processing system. Forexample, similar rotation or position errors among a plurality ofpositioning features can indicate an overall rotation or position errorin placement of the substrate. Different rotation or position errors canindicate distortion of a substrate, or misplacement of positioningfeatures on the substrate. The method 500, and variations thereof, areperformed using a digital processing system programmed with instructionsappropriate to render the various coordinates and calculations referredto in the method 500. The digital processing system accepts datarepresenting the image from the imaging unit, and automaticallyidentifies the boundaries of the feature in the image, and optionallythe position error, the rotation error and the mis-shape error of thepositioning feature in the image. The results of the method 500 can beused to control precision deposition of material onto a substrate using,for example, the deposition apparatus 100 of FIG. 1 .

FIG. 6 is an isometric top view of a deposition device according toanother embodiment. The device of FIG. 6 is similar to the device ofFIG. 1 , with the difference that the laser imaging system 150 isabsent. Instead, a first laser imaging system 650 is movably coupled toan imaging rail 604, which is part of a deposition assembly support 616.The deposition assembly support 616 is like the deposition assemblysupport 116 of FIG. 1 , including the beam or rail 117, which is adeposition rail in this case. The deposition assembly support 616include an extension 620 that supports a first imaging system 650 and asecond imaging system 652. The extension 620 comprises a first riser 622that extends from a first end 624 of the deposition rail 117 and asecond riser 626 that extends from a second end 628 of the depositionrail 117 opposite from the first end 624. The extension 620 furthercomprises the imaging rail 604, which extends from the first riser 622to the second riser 624, substantially parallel to the deposition rail117.

Each of the first imaging system 650 and the second imaging system 652is substantially the same as the imaging system 150. The first imagingsystem 650 is coupled to the imaging rail 604 by a first imagingcarriage 654. The second imaging system 652 is coupled to the imagingrail 604 by a second imaging carriage 656. The dispenser housing 119 isbetween the first imaging system 650 and the second imaging system 652.Each of the first imaging carriage 654 and the second imaging carriage656 has a lateral extension that supports the first and second imagingsystems 650 and 652 at a clearance from the imaging rail 604. Theclearance allows each of the first and second imaging systems 650 and652 to move along substantially the entire length of the imaging rail604, with no interference from the deposition housing 119.

The device 600 has four independently movable imaging systems. The twoimaging systems 650 and 652 described above are located on a first sideof the deposition support assembly 616. The device 600 has a thirdimaging system 660 and a fourth imaging system 662, each of which is alaser imaging system like the imaging systems 650 and 652. Here, theimaging rail 604 is a first imaging rail, and a second imaging rail 664is part of the deposition support assembly 616. The first and secondimaging rails 604 and 664, in this case, are both disposed on the tworisers 622 and 626, and extend parallel, each to the other, between thetwo risers 622 and 626. The imaging systems 660 and 662 are eachsupported on the second imaging rail 664 by an imaging carriage.Specifically, a third imaging carriage 674 couples with the secondimaging rail 664 to support the third imaging system 660, and a fourthimaging carriage 676 couples with the second imaging rail 664 to supportthe fourth imaging system 662. A space between the imaging rails 604 and664 allows the first and second carriages 654 and 656 to move along thefirst imaging rail 604 without interference from the third and fourthcarriages 674 and 676. In this way, all four imaging systems can bepositioned along substantially the entire length of the depositionsupport assembly 616. Use of multiple imaging systems allows for a highvolume of images to be captured in a smaller time, thus speeding upprocesses that depend on such imaging.

Any number of the laser imaging systems described herein can be usedwith such a device. In FIG. 6 , four imaging systems are illustrated,but any number of such imaging systems can be used. For example, twoimaging systems can be used on one of the two imaging rails, or twoimaging systems can be used, one on each imaging rail. Imaging systemscan be added to one or both imaging rails by merely placing the carriageof an imaging system on the desired imaging rail. In some cases, thecarriages couple to the imaging rails using air bearings, so the airbearing of the added imaging system can be activated to allow the addedimaging system to move along the chosen imaging rail. Deploying aplurality of laser imaging systems allows a device to use the imagingprecision of laser radiation to image a plurality of locationssimultaneously, thus increasing the speed of imaging various portions ofa substrate. Using multiple imaging devices can also increase precisionof imaging at a single location on the substrate if two or more imagesof the location are acquired and compared.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the present disclosure may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method of imaging a feature on a substrate, comprising: relativelyscanning a substrate and a laser imaging system comprising a lasersource and an imaging unit; activating the imaging unit before anextremity of a feature of the substrate to be imaged reaches anillumination field of the laser source; activating the laser source whena portion of the feature reaches the illumination field; deactivatingthe laser source after an active time; and deactivating the imagingsource after an imaging time, wherein the imaging time encompasses theactive time.
 2. The method of claim 1, wherein the active time is lessthan 5 μsec.
 3. The method of claim 2, wherein the imaging unit is acamera having sensitivity matched to the emission wavelength of thelaser source.
 4. The method of claim 3, further comprising relativelypositioning the substrate and the laser imaging system based on anexpected location of the feature.
 5. The method of claim 4, furthercomprising automatically identifying a boundary of the feature in theimage.
 6. The method of claim 4, further comprising automaticallyidentifying a position error of the feature.
 7. The method of claim 4,further comprising automatically identifying a rotation error of thefeature.
 8. The method of claim 1, wherein the laser imaging system is afirst laser imaging system, and further comprising: capturing a firstimage of the feature using the first laser imaging system; and capturinga second image of the feature using a second laser imaging system. 9.The method of claim 8, wherein the first laser imaging system and thesecond laser imaging system are coupled to a support extending across asubstrate support on which the substrate is disposed for imaging.
 10. Amethod, comprising: relatively scanning a substrate and a laser imagingsystem comprising a fiber-coupled laser source and an imaging unit;activating the imaging unit before an extremity of a feature of thesubstrate to be imaged reaches an illumination field of the lasersource; activating the laser source when a portion of the featurereaches the illumination field; capturing an image of the feature whilethe laser source is activated; deactivating the laser source after anactive time; and deactivating the imaging source after an imaging time,wherein the imaging time encompasses the active time.
 11. The method ofclaim 10, wherein the laser imaging system is coupled to a depositionassembly of a deposition device, and relatively scanning the substrateand the laser imaging system comprises moving the substrate during theactive time.
 12. The method of claim 10, wherein the imaging unit is acamera having sensitivity matched to the emission wavelength of thelaser source.
 13. The method of claim 10, further comprisingautomatically identifying a boundary of the feature in the image,automatically identifying a position error of the feature, automaticallyidentifying a rotation error of the feature, or any combination thereof.14. The method of claim 10, further comprising determining when toactivate the imaging unit and the laser source based on an expectedposition of the feature on the substrate and a movement rate of thesubstrate.
 15. The method of claim 14, further comprising using asubstrate holder to move the substrate and determining a movement rateof the substrate based on signals from the substrate holder.
 16. Themethod of claim 13, wherein automatically identifying a boundary of thefeature in the image comprises analyzing brightness of pixels of theimage.
 17. The method of claim 10, wherein the image of the feature iscaptured while the substrate and the laser imaging system are inrelative motion.
 18. The method of claim 10, wherein the active time isa time during which the feature is within the illumination field.
 19. Amethod, comprising: relatively scanning a substrate and a laser imagingsystem comprising a fiber-coupled laser source and an imaging unit;activating the imaging unit before an extremity of a feature of thesubstrate to be imaged reaches an illumination field of the lasersource; activating the laser source when a portion of the featurereaches the illumination field; capturing an image of the feature whilethe feature is located within the illumination field; deactivating thelaser source after an active time; and deactivating the imaging sourceafter an imaging time, wherein the imaging time encompasses the activetime.
 20. The method of claim 19, wherein the image of the feature iscaptured while the substrate and the laser imaging system are inrelative motion.